The present invention relates generally to computer image generation systems and, more particularly, to a method for real-time color modulating display pixels for cell texturing.
One application for real-time computer image generation has been for visual training simulators that present scenes to an operator or trainee for practicing a task, such as piloting an airplane. In a visual training simulator, a three-dimensional model of the desired gaming area is prepared and stored on magnetic disk or other bulk storage medium. This model is designated the visual data base. A visual simulator combines an image generator with an electro-optical display system, such as a cathode ray tube (CRT) or similar display. The image generator receives three-dimensional data from the storage medium and transforms these data into corresponding perspective compensated two dimensional scene descriptions for display. The displayed image is representative of the scene that the operator would see if the operator were actually performing the task being simulated. Generation of the display images is said to be in "real time", which is normally taken to mean 30 frames per second, as in the U.S. television standard. Computer image generation systems are described in a book entitled Computer Image Generation, edited by Bruce J. Schacter and published by Wiley-Interscience (1983).
One known system is described in U.S. Pat. No. 4,343,037 to Bolton. According to the Bolton patent, a texture pattern is stored in memory and retrieved for each pixel along each scan line. (A plurality of scan lines form a frame. In a rectangular raster scan used by the U.S. television industry, 525 scan lines constitute one complete frame.) However, due to practical memory size limitations and to access times required for retrieving stored data from memory, the level of detail (LOD) which can be handled in real time by the Bolton system is limited. For depicting images of complex objects, such as trees, the number of edges and texture patterns required to generate a realistic or suitable image is considered to be prohibitively large for achieving feasible real time response in a system configured in accordance with the teachings of the Bolton patent.
Cell Texture image modulation described in the Bunker et al application uses monochrome modulation of an existing data base face color that is combined with face translucency information. That is, the cell texture processing for each cell is controlled by the intensity of a composite color assigned to and corresponding translucency of a face. True full color cell texture modulation could be produced by sequentially processing three faces, each face being assigned one of the triad of primary colors (i.e. red, green, blue; hereinafter "RGB"), with appropriate intensity and translucency obtained from the texture map for each cell. However, this approach would be very inefficient. Such processing would consume a large portion of available real time image processing capability. Furthermore, a straightforward modification to add true full color cell modulation to the configuration of Bunker et al would require a substantial increase in cell texture hardware.
While some previous systems have permitted simultaneous but equal modulation of all RGB components of a pixel (i.e., monochrome modulation), it was not practical prior to the present invention to have individualized independent true full color modulation of each of the respective RGB components for cell texturing in a real time image generation system. True full color modulation as used herein may be described as the ability to control the RGB components by independently modulating the RGB components using a single texture code so that a realistic color image may be displayed on a single face.
It is therefore an object of the present invention to provide real-time computer image generation with true full color cell texture modulation.
It is another object of the invention to provide a real time video image generator with true full color cell texture modulation while minimizing hardware requirements.